Applications of positron annihilation spectroscopy and molecular dynamics simulation to aromatic polyamide pervaporation membranes

On the structure and rejection of ions by a polyamide membrane in pressure-driven molecular dynamics simulations

“…Molecular dynamics (MD) is an attractive technique for gaining insights into RO membrane features such as polymer configuration, free volume distribution, and transport phenomena [8][9][10][11]. Indeed, it offers unique opportunities to connect some macroscopic properties to a microscopic description of the physical phenomena involved in the separation.…”

Molecular Scale Modeling of Membrane Water Treatment Processes

“…Several recent publications have addressed the role of the fractional free volume (FFV) on the performance (water and salt transport) of various PA membranes as determined from MD simulations [34,37,38]. The FFV is proportional to V − V 0 /V, where V is the total system (model) volume, V 0 is the specific volume CV w , where V w is the van der Waals space of the polymer and C is a proportionality constant whose value depends on the type of hard-surface probe rendering implemented (typically a Connolly surface with a probe radius of 1.3-1.6Å; Figure 10.13).…”

“…Kao et al [37] found that for aromatic PA pervaporation membranes used for ethanol separations, the FFV could be increased by direct incorporation of bulky monomer groups (e.g., 1,4-bis[4-aminophenoxy]2,5-di-tert-butylbenzene or arylene ether groups) into the polymer backbone. MD simulations of the various novel polymer systems were able to predict FFVs that closely correlated with experimental values determined from PALS.…”

Free volume and polymeric structure analyses of aromatic polyamide membranes: A molecular simulation and experimental study

“…Moreover, the sorption of alcohol on the PA membranes is also discussed using the MC method for a further understanding of the alcohol-membrane interaction. To validate the feasibility and accuracy of the present simulation work, all of the calculated results were compared with the experimental data of Teng et al [21] and Kao et al [22].…”

“…Teng et al [21] also fabricated aromatic polyamide (PA) membranes containing different quantities of bulky side groups to increase the permeation rate in PV for high purity alcohol production. In addition, Kao et al [22] analyzed the free volume distribution of these PA membranes at the microscale using the positron annihilation lifetime spectroscopy (PALS) technique. The longer lifetime ( 3 ) and higher intensity (I 3 ) of o-Ps annihilation observed in the PA membrane with more bulky groups validate the effect of side chain occupancy on the free volume size distribution.…”